In the front-end of the radio frequency (RF) circuit, the VCO is utilized to provide a precise local oscillation signal to the mixer to transform the signal into an RF signal or transform the signal to an intermediate frequency (IF) signal.
The phase noise may have a strong effect on the output signal of the VCO. Therefore, if the phase noise is reduced, the burden on the next stage circuit behind the VCO will be decreased. In the prior art, there are two methods to reduce the phase noise of the VCO. One method is by increasing the Q value (quality parameter of the inductor) of the inductor and the other method is by increasing the output power. However, in the method for increasing the Q value of the general transformer inductor, the larger area may need to be configured for the inductor. In addition, the method for increasing the output power may use more power.